On my situation, there is a big difference. Very big. Got destroyed on Mycomancer Cavern’s Bogpiper on first run wasted all my Life’s and was just doing 1 group of mobs at one time.
On a separate run, I completed the whole thing without a Death and I was pulling 2 groups at a time… even accidentally pulled a 3rd group and I was still able to mow them down. Both scenarios, I was doing the same strat… using all my defensives, all my nuke cd’s , interrupts, stuns, mass stuns ,etc. But the later setup is more smooth and easier.
That’s all a player needs. Yes, they also need to learn what their class/spec can do and when to do it, but just as importantly is when to move and keeping in tune with the enemies spell casts and swirlies on the ground.